winkler



July 4, 1950 A. H. WINKLER 2,513,833

PUMP

Filed Sept. 2, 1945 4 Sheets-Sheet 1 2a O 5o 40 24 25 42 a 52 4A 63/ 49 W A A 3 1 5a I 1 L I: I l 48 I 32 34 7 30a. 28 54 5a i 74 F] g. E

INVENTOR BYALBEET h. M/V/(LER y 4, 1950 A. H. WINKLER 2,513,833

PUMP

Filed Sept. 2, 1943 4 Sheets$heet 5 200 a O 202 0 l l INVENTOR ALBERT H W/A/KLE/a Patented July 4, 1950 PUMP Albert H. Winkler, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application September 2, 1943, Serial No. 500,893

11 Claims.

This invention relates generally to fluid pumps and has particular reference to positive displacement pumps.

While the invention in its broader aspects may be incorporated in pumps of various types and for various purposes it will be shown and described herein, incorporated in pumps of the positive pressure type for supplying fuel to charge forming devices or carburetors and the like. In many carburetors it is necessary to supply the fuel thereto under superatmospheric pressure and at a substantially constant pressure. There are various well known pumps wherein various means have been proposed for meeting the foregoing requirements of a fuel pump for carburetors and among these it is well known to use a controlled fuel by-pass from the discharge side to the inlet side of the pump. There are numerous variations of such a by-pass system but these various arrangements have certain disadvantages particularly when the fuel being pumped is a high grade, highly volatile gasoline. For example, the fuel thus by-passed is churned considerably which often results in the formation of a substantial amount of vapor which frequently results in a vapor lock and/or other well known difficulties.

It is therefore an important object of the present invention to provide a pump adapted to pump highly volatile fluids, which will overcome the above mentioned difiiculties.

It is another object of the invention to provide a positive displacement pump having an expansible pumping chamber to accommodate fluid which is not discharged from the pumping chamber due to restriction or complete closing of the discharge passage of said pump.

Still another object of the invention is to provide a device of this character wherein one wall of the expansible chamber is movable and which, if desired, may comprise a flexible diaphragm.

It is still another object of the invention to provide a device of this character wherein there is means for preventing oscillation of the flexible portions of the diaphragm such as would adversely affect the intake of fuel into the pump or prevent such intake of fuel.

A further object of the invention is to provide a pump of this character wherein the expansible chamber has a movable member or wall which is connected to and controls the outlet check valve, the position of said movable member bein determined by the quantity of fuel in said chamber.

A still further object of the invention is to provide a device of this character wherein the pump is operable independently of the direction of rotation of the drive shaft thereof.

It is a still further object of the invention to provide a device of this character wherein the inlet check valve is carried by a pumping member. Another object of the invention is to provide a device of this character wherein there is means for effecting rapid filling of the pump chamber v or chambers when the pump is started empty.

Still another object of the invention is to provide a positive displacement pump of the rotary type having a plurality of sliding vanes urged against the rotor by outlet fluid pressure which is of substantially a constant value.

A further object of the invention is to provide a device of this character that is simple in construction and reliable in operation.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the following detailed description of the accompanying drawings, which represent a preferred embodiment of the invention and certain modifications thereof. After considering these examples, skilled persons will understand that many variations may be made without departing from the principles disclosed; and I contemplate the employment of any structures, arrangements, or modes of operation that are properly within the scope of the appended claims.

In the drawings:

Figure 1 is a diagrammatic view of a fuel system embodying the present invention;

Figure 2 is a section through a fluid pump embodying the invention;

Figure 3 is a section taken on line 33 of Figure 2;

Figure 4 is a view partially in section of a modified form of the invention;

Figure 5 is a view partially in section of another embodiment of the invention;

Figure 6 is a section taken on line 66 of Figure 5; and

Figure 7 is a section taken on line I-'! of Figure 5.

Throughout the drawings similar reference characters refer to similar parts except where said parts are modified in structure and function, in which case they are given further differing reference characters.

Referring first to Figure 1 there is shown a fuel system for internal combustion engines which includes a fuel tank 10 having a pipe connection I 2 with a carburetor M, the fuel being delivered to the carburetor under substantially constant pressure by a power driven pump l6 of the positive displacement type which is interposed in the pipe I2. A wobble pump 18, of any well known type, is also interposed in the pipe l2, between the tank I 0 and the pump it. A by-pass I1 is provided around the pump [8 with a valve l9 to permit flow of fuel from the tank II] to the pump l6 at such times as the wobble pump I8 is not being operated.

Referring to Figures 2 and 3 there is shown a power driven positive displacement pump of the rotary type in which the present invention is embodied, said pump comprising a body or stator 20 having a cylinder 22 in which is rotatably mounted a rotor 24. The rotor is attached to a shaft 26 journalled in the body 20 concentric with the cylinder 22 and connected to a suitable source of power, not shown, said rotor being eccentric to the axis of the shaft 26. It is to be noted that the point, indicated at L, which represents the point of the eccentric rotor most closely adjacent the wall of the cylinder, does not actually contact said wall. The body 20 is provided with diametrically opposed slots 28 and 30 which open into the cylinder 22 and in which are slidably received sliding vanes 32 and 34 respectively which are urged inwardly into contact with the rotor 24 by springs 36 and 38 respectively. These vanes divide the cylinder 22 into two pumping chambers, 25 and 21, each of which is provided with an inlet passage 40 and an outlet passage 42. Each inlet passage includes a cylindrical chamber 44 connected by a passage 46 with an inlet 48 adapted to be connected with a source of fuel, said passages 46 and inlet 48 being in a head 41 secured to the body 20 by screws 49. In each chamber 44 is a piston-like member 50 which is slidable therein and urged to the right, as shown in Figure 2, by a calibrated preloaded spring 52 which reacts between the piston assembly and the left-hand end of the cylinder 44 to urge the piston to the right against shoulder 53 which acts as a stop. The respective pistons 50 are provided with a central bore 54 which provides a fuel passage therethrough controlled by an inlet check valve member 56 of well known character disposed in an enlarged portion of bore 54 of the piston 50. The check valves 56 are provided with seats 51 and are adapted to permit the flow of fuel through the pistons and into the respective chambers 25 and 21 of the pump and to prevent a reverse flow of fuel through said pistons. Piston seals 58, of any suitable character, are received in annular grooves in the pistons and are retained in place by ring-like members 60 pressed onto reduced end portions of the pistons 58, said seals being adapted to minimize the escape of fuel past the pistons. The respective outlet passages 42 are controlled by outlet check valves of any well known character which, as shown comprise plugs 84 having fuel passages 63 therethrough controlled by valve members 62 of well known character which are disposed in the plugs 63 and cooperate with valve seats 66. The check valves 62 are adapted to permit fuel to be discharged from the respective pump chambers and to prevent a return flow of fuel through the passages 42. A head member 68 is secured to the body 20 by screws 10 and said member 68 is provided with an outlet passage I2 having branches 14 connected with the respective passages 42, the outlet I2 being adapted to be connected with a carburetor or other device to be supplied with fuel. If desired there may also be connections 28a and 30a between the inlet 48 and outlet I2 and slots 28 and 30 respectively whereby the respective vanes 32 and 34 are subjected to inlet and outlet fuel pressure to aid in urging said vanes against the rotor 24.

Means may be provided for sealing the shaft 26, which is journalled in an extension I6 of the body 20, to minimize the loss of fluid therepast. The sealing means may be of any well known character, being shown as comprising a flexible diaphragm 18 of suitable characteristics which is marginally clamped between a shoulder in the extension I6 and an annular ring which is received in .an annular chamber 82 through which the shaft 26 extends. A sleeve 84 is received on a reduced portion 86 of the shaft and abuts against a shoulder 88 at the junction of the reduced portion 86 with the larger portion of the shaft 26. Said sleeve 84 is provided with a shoulder and a central portion of the diaphragm I8 is clamped between said shoulder and a retaining ring 90 which is pressed onto the sleeve 84. A plate 92 .closes the outer end of the chamber 82 and is secured by screws 94. The plate has an annular flange 96 which extends into the chamber 82 and urges the ring 80 tightly against the diaphragm I8 thereby firmly securing the marginal portion of the diaphragm, and a spring 98, reacting between the plate 92 and the retaining ring 98, urges the sleeve 84 against the shoulder 88. Should any fuel escape past the seal into the chamber 82 said fuel is drained away through orifices I00 in the flange 96 into an annular passage I02 and thence through passage I 04. The passage I04 is connected with a threaded drain outlet I06 which may have pipe connections, not shown, for carrying away and suitably disposing of the fuel which has leaked past the seal.

Operation of the device shown in Figures 2 and 3.--Fuel supplied to the inlet 48 is dicharged from the outlet 12 and while the functioning of the pump is independent of the direction of rotation of the eccentric rotor 24 it will be assumed that the direction of rotation of said rotor is clockwise. With the point L, representing the point on the rotor most closely adjacent to the wall of the cylinder 22, in its uppermost position (after 90 rotation from the position shown) the volume of the upper chamber 25 is at a minimum and that of the lower chamber 21 is at a maximum. As the point L rotates to its lowermost position the volume of chamber 25 increases to its maximum, drawing fuel past the respective inlet check valve 56, and the volume of chamber 21 decreases to its minimum, pumping fuel past the respective outlet check valve 62 through the outlet I2. During the next 180 of rotation, fuel is pumped from chamber 25 and more fuel is drawn into chamber 21.

With the arrangement shown, the pump produces a substantially constant discharge pressure over the inlet pressure, said discharge pressure depending upon the strength of said springs 52 which are so calibrated that when the pump is operating between zero discharge and a discharge closely approaching maximum capacity there is sufficient pressure in the pumping chambers 25 and 21 to force the pistons 50 to the right an amount determined by the degree of restriction of the outlet. That is, should the flow of fuel from the outlet I2 be entirely out off the pistons 50 will merely move back and forth so as to maintain the volume trapped between the inlet and outlet valves constant notwithstanding rotation of the rotor 24. The fuel thus oscillates back and forth between the chambers 25 and 21 and the cylinders 44 respectively thus eliminating bypassing of the fuel from the high pressure side to the low pressure side of the pump which action tends to produce vapor on the suction side of said pump. At rates of fuel flow below that closely approaching maximum, the pressure developed in the respective chambers 25 and 21 forces the pistons 50 to the left sufficiently to take care of the difference between the normal decrease in the volume of the chambers 25 and 21 and the quantity of fuel being discharged per revolution of the rotor.

In the arrangement shown in Figure 4, diaphragms are used to form movable walls of the pumping chambers in place of the pistons 50 of Figure 1. This arrangement is particularly applicable where fuel is supplied to the pump under superatmospheric pressure which pressure will tend to maintain the flexible portions of the diaphragms outwardly, as shown in said Figure 4,

during the intake period of the pump. In this embodiment the inlet check valves are of any well known type, being shown as comprising threaded plugs M in inlet passages-43 and having valve members 45 cooperating with valve seats The inlet valves are adapted to permit fluid to enter the pump chambers25 and 21 and prevent flow of fluid in the opposite direction. The expansion chambers, indicated generally at 53,

portion I36 somewhat larger than the portion I34, and a still larger portion I38 into which the inner end of shaft I26 extends, the portion I38 being of sufficient size to permit reciprocation of the piston I24 without having the latter strike the shaft I26. The outer end of shaft I26 is notched to receive a flattened extension I40 of a driver shaft I42 thereby forming a suitable connection between said shafts I26 and I42. The latter shaft is journalled in a plate I44 attached to the body I20 of the pump by screws I46 and a seal I48 of any well known character may be provided to minimize the loss of fuel between have connections 55 with the respective pumping I chambers and 21. Each expansion chamber includes a casing 51 in which a flexible diaphragm 59 is mounted and is urged by a spring 6| in a direction to reduce the size of the pumping chamber, its movement in said direction being limited by a stop member 63. One side of each of the diaphragms 59, which may be considered the inner side, is adapted to be subjected to fluid pressure from the pump chamber with which the expansion chamber is connected and the opposite or outer sides of the diaphragms may be connected by a conduit 65 with atmosphere, a supercharger, air scoop or the like so that it is at all times properly balanced and therefore unaffected by changes in pressure occurring at the inlet opening of the carburetor or the like being supplied with fuel by the pump.

In this embodiment of the invention the back ends of the vanes 32 and 34 are subjected to the pump outlet pressure there being a fluid connection 61 between the outlet 12 and the outer or rear end of the slot' to the rear of the vane 34 and also a fluid connection 69 between the rear end of the slot 30 and the corresponding portion of the slot 28 of vane 32. With this arrangement the back ends of both vanes during normal operation will be subjected to the substantially constant outlet fluid pressure of the pump, and variations in pressure at the intake 48 will not affect the force with which the vane 32 is held against the rotor, an arrangement that may be particularly desirable where the source of fuel for the pump is at a lower level than said pump and the latter draws fuel from said source by suction.

.Referring to the embodiment shown in Figures 5, 6 and 7 there is disclosed a reciprocating type of pump which includes a body portion I20 having a cylinder I22 in which a piston or pumping member I24 is reciprocably disposed. The piston may be reciprocated by any suitable means, the means herein shown by way of example comprising a shaft I26 mounted in a bearing I28 fixed in the body I20, said shaft having an extension I30 of reduced size and eccentric relative to the axis of said shaft I26. The extension is received in a cross bore of a cylindrical member I32 received in an opening extending diametrically through the piston I24, an arrangement adapted to accommodate the reciprocating motion and any slight misalignments of the parts. It is to be noted that the diametrical opening of the piston is stepped and includes a portion I34 of substantially the same size as the diameter of the reduced portion I30 of shaft I26, an intermediate v valve.

shaft I26 and bearing I28. However, should fuel escape past the seal I48 it may be drained away through a drain outlet I50 and drain pipe I52 which may be connected thereto.

Fuel is supplied to the pump by way of a fuel inlet I54, connected with a. fuel supply conduit I50 from a suitable source of fuel, and said fuel passes into an annular groove I58 in the piston I24 intermediate the ends thereof. The pump is of double acting type but inasmuch as each side is constructed and operates in the same manner a description will be made of but the left hand side as shown in Figure 5. The annular groove I58 is connected with an axial chamber I62 by passages I60 the outlet of which is controlled by an inlet check valve I64 urged closed by a spring I66 reacting between a head I68 on valve stem I10 and a valve support and guide I12. An outlet check valve I14, of larger diameter than the cylinder, closes the outer end of said cylinder 122 and provides a movable wall for a chamber 2I0, the other walls of said chamber being the adjacent end of the cylinder I22 and the piston. An outwardly extending flange I16 is provided about the open end of the valve I14 and is adapted to seat on an annular gasket I18 secured in a groove in the body I20, said gasket being of fiber, neoprene or any other suitable material. The valve I14 is secured to a flexible diaphragm I by means of a rivet I82, there being a reinforcing plate I84 secured by said rivet I82 to the diaphragm on the side thereof opposite the It is to be noted that the marginal edge portion of the plate I84 is turned laterally away in the diaphragm to protect the latter from being cut or otherwise injured by the edge of said plate. The diaphragm is marginally secured between the outer end of a wall I81 and a cap I thereby forming an expansion chamber I88 which may be considered as extending between the valve seat portion I18 and said diaphragm I80. The cap I90 is cup-shaped to provide a spring chamber I92 in which is disposed a spring I94 adapted to react between the cap and the plate I84 for urging the valve I14 to the closed position. If desired the chamber I92 may be in communication with the atmosphere, an air scoop, supercharger or the like by means of a connection I96, so that the valve I14 is at all times properly balanced and therefore the relative fuel pressure is unaffected by changes in pressure occurring at the inlet opening of the carburetor being supplied with fuel by the pump. The chamber I88 is connected by a passage I98 with an outlet 200 which may be connected with a discharge conduit 202.

If desired a by-pass may be provided around the outlet check valve I14 which includes a passage 204 connecting chambers 2H] and I88 and is controlled by a ball check valve 206 received in an enlargement 201 of the passage 204 and 75 urged to the closed position by a spring 208. ,The

purpose of this by-pass will be hereinafter described.

Operation of the embodiment shown in Figures 5, 6 and 7.This embodiment of the device is also operable independent of the direction of rotation of the drum shaft, the pump being double acting and of a positive displacement type. Upon rotation of shaft I26 the piston is reciprocated in the cylinder I22. During the intake stroke of the piston fuel is drawn into the inlet I54, groove I58, passage I60, chamber I62 and the chamber 2I0 between the outlet check valve I14 and the adjacent end of the piston I24, the outlet check valve I14 being closed and the inlet check valve I64 opening to admit fuel into said chamber 2I0. When the piston reaches the end of its intake stroke the inlet valve I64 is closed by spring I66 and as the piston moves through its discharge stroke the pressure of fuel in chamber 2I0 forces the outlet check valve I14 to the left, as shown in Figure 5, forcing said fuel past said outlet valve I14 into the chamber I88 and thence through passage I98 and the outlet 200. This cycle of operation will occur and the pump will discharge at its full capacity as long as the outlet is unrestricted. It will be understood that under such operating conditions the diaphragm I80 will be forced outwardly a limited extent. Should the outlet be partially restricted so that there is but a limited discharge of fuel the pressure developed in chambers 2I0 and I88 force the diaphragm I80 further to the left during the discharge stroke of the piston, the outward movement of the diaphragm effecting an enlargement of chamber I88 suflicient to take care of the difference between the normal decrease in the volume of chamber 2I0 and the quantity of fuel discharged per discharge stroke of the piston. In-

asmuch as the outlet valve is controlled by the movable wall or diaphragm I80 the quantity of fuel drawn into the pump by the intake stroke of the piston will depend on the quantity of fuel in chambers I88 and 2I0. For example, should the outlet of the pump be restricted so that but one half of the maximum capacity thereof be discharged the remaining half of the fuel will remain in chambers I88 and 2I0 and no additional fuel will be drawn into the pump cylinder until the piston has traveled through the initial half of its intake stroke during which the excess fuel in chambers I88 and 2I0 will be returned to the cylinder under the force of spring I94. When this excess fuel has been returned to said cylinder the diaphragm has reached a position where the valve I14 is closed, Thereafter said valve provides an inflexible end wall for the cylinder and further movement of the piston on its intake stroke will draw more fuel into the pump. Should the flow from the outlet 200 be entirely out off the diaphragm I80 would merely oscillate back and forth so as to maintain the volume trapped in chambers 2I0 and I80 constant notwithstanding the reciprocating action of the piston. In this embodiment of the invention it is to be noted that the outlet check valve is anterior to the expansion chamber I88 and that the position of the diaphragm controls the position of the outlet check valve I14, the position of said diaphragm being, of course, determined by the quantity or volume of fuel discharged through chamber I88. It is to be further noted that certain difficulties may be encountered in devices of this character when a diaphragm is used as one wall of the expansion chamber and the fuel is drawn from a source by the pump suction.

These diflicultles arise from the tendency of portions of the diaphragm between the centrally reinforced portion and the marginally clamped portion and which are extremely flexible, to oscillate back and forth and prevent the building up of pressure for the discharge of fuel from the pump, and the intake of fuel during the intake stroke of the piston. By providing the large valve I14 such as shown in Figure 5, an inflexible end wall is provided for the chamber 2 I0, so that the fuel will be drawn into said chamber during the intake stroke of the piston, otherwise during said intake stroke of the piston the above mentioned flexible portion of the diaphragm would merely be drawn toward the retreating piston and preventing establishment of the necessary vacuum for drawing more fuel into the pump and during the discharge stroke said portions of the diaphragm would be forced outwardly and there would be no discharge of fuel.

The purpose of the by-pass 204 is to provide means whereby the pump may be rapidly filled with fuel when started without any fuel therein. The spring I94 for the outlet check valve I14 is calibrated for a predetermined pump outlet pressure which may be of such a value that the air in chamber 2I0 cannot be compressed sufliciently to force open the valve I14. In order to overcome this difficulty the spring 208, controlling the by-pass valve 206, is substantially weaker than the spring I94 so that a substantially lower air pressure in the chamber 2I0 will force open the valve 206 with each discharge stroke of the piston and drive out a suificient quantity of air to render the pump effective. The by-pass 204 as shown is of relatively small effective capacity but if desired may be of sufficiently large capacity as to serve as a fuel bypass should the pump stop operating, fuel being then forced to the carburetor by the wobble pump. In either event the bypass will not adversely affect the effectiveness of the pump when pumping fuel due to the fact that once fuel is being pumped the pressures in chambers I88 and 2I0 during the pumping stroke are substantially equal and during the intake stroke both valve I14 and valve 206 are closed.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and though said invention has been illustrated and described in connection with a preferred embodiment and several modifications thereof it will be apparent that various other changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the forms hereinbefore described being merely preferred embodiments.

I claim:

1. In a double acting rotary pump: a stator; a rotor therein eccentric with the axis thereof; means engageable with the periphery of the rotor for dividing the stator into a plurality of pumping chambers; an inlet passage for each of the pumping chambers including a cylindrical portion; a piston yieldingly urged in the direction of fuel flow in each of said cylindrical portions; inlet fuel passages in said pistons; inlet valves carried by said pistons and controlling said fuel passages; and outlet valves for each of said pumping chambers.

2. In a pump for a supercharged carburetor: a pumping chamber; a pumping member therefor;

an expansible chamber connected with the pump- T ing chamber; a movable wall in the expansible chamber one side of which is adapted to be subjected to the pressure in the pumping chamber, and means for venting the opposite side of the movable wall to supercharger discharge pressure.

3. In a rotary pump: a stator having a cylinder therein; a rotor eccentrically mounted in the cylinder and having the point closest to the cylinder Wall spaced therefrom; oppositely disposed sliding vanes each contacting the surface of the rotor; springs urging the inner ends of the vanes into contact with the rotor and dividing the cylinder into two pumping chambers; an inlet passage branching into the respective pumping chambers and including cylindrical portions; a connection with the inlet passage arranged to subject the outer end of one vane to the pressure of fluid in said inlet passage; a piston in the cylinder portion in each branch of the inlet passage; a bore through each piston controlled by an inlet valve; calibrated springs urging the pistons in the direction of fluid flow; outlet passages for each of the pumping chambers; and means for subjecting the outer end of the other vane to the outlet pressure of the pump.

4. In a rotary positive pressure pump: a stator; a rotor therein and eccentric thereto, the point of the rotor closest to the Wall of the stator being spaced therefrom; oppositely disposed slidable vanes having ends adapted to engage the periphery of the rotor and divide the stator into a plurality of depression chambers; valve controlled inlet and outlet passages for the pumping chambers; means for subjecting the outer ends of the vanes to the pump outlet pressure; an expansible chamber connected with each of the pumping chambers; said expansible chambers having a wall comprising a flexible diaphragm one side of which is adapted to be subjected to the pressure in the respective pumping chamber and the opposite side being adapted to be subjected to air pressure; a spring in each expansible chamber adapted to urge the respective diaphragm in a direction to reduce the volume of said chamber; and means in each chamber adapted to limit the spring urged movement of the diaphragm.

5. In a fluid pump: a pumping chamber; a pumping member therefor; inlet and outlet passages for the pumping chamber; inlet and outlet valves for said passages; an expansible chamber communicating with the pumping chamber; said expansible chamber including a movable wall; means for controlling the outlet valve in accordance with the quantity of fluid in the expansible chamber; and means for venting the back of the movable wall to a source of air pressure.

6. In a rotary pump for fluids: a stator; a rotor therein; means providing a pumping chamber between the stator and the rotor; means defining an expansion chamber in communication with the pumping chamber, and a spring-loaded flexible diaphragm forming a movable wall of said expansion chamber and adapted to respond to a predetermined pressure condition in the pumping chamber.

7. A fluid pump comprising a pump body, a cylindrical pump chamber in said body, an eccentric rotor mounted in said chamber, a plurality of movable vanes mounted in said body and adapted to engage the periphery of said rotor and thereby to divide the chamber about said rotor into a plurality of compartments, a valve controlled fluid inlet for each of said compartments, a valve controlled fluid outlet for each of said compartments, and an expansible chamber for each of said compartments adapted to accommodate fluid not discharged from said compartments during the discharge stroke of said rotor.

8. A fluid pump comprising a pump body, a

cylindrical pump chamber in said body, an ec- I centric rotor mounted in said chamber and journaled concentrically with the axis thereof, a plurality of movable vanes mounted in said body and adapted to engage the periphery of said rotor and thereby to divide the chamber about said rotor into a plurality of compartments, a valve controlled fluid inlet for each of said compartments, a valve controlled fluid outlet for each of said compartments, an expansible chamber including a movable wall, and a calibrated yieldable means adapted to urge the said movable Wall in the direction to reduce the size of the expansible chamber and thereby to maintain the discharge pressure of the pump at a substantially constant predetermined value.

9. In a fluid pump: a pumping chamber; a pumping member adapted to vary the size of the pumping chamber; an expansible chamber communicating with said pumping chamber and having a movable wall; and a fluid passage for said pumping chamber having a valve therein operatively connected to said wall and adapted to respond to the movement thereof.

10. In a constant pressure fuel pump: a pumping chamber; a pumping member operatively associated with said chamber; an expansible chamber communicating with said pumping chamber including a movable wall; a calibrated yieldable means for urging said wall in the direction to reduce the size of said expansible chamber; and an inlet valve for said pumping chamber operatively connected to said wall and adapted to respond to the movement thereof.

11. In a fluid pump: a pumping chamber; a pumping member therefor; an inlet and an outlet passage for said chamber; a chamber forming a portion of said inlet passage; 3, spring-loaded piston reciprocable in said last mentioned chamber; an inlet valve in said piston; and an outlet valve in said outlet passage.

ALBERT H. WINKLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 678,338 Harger July 9, 1901 725,707 Hoffman Apr. 21, 1903 985,013 Dismond Feb. 21, 1911 1,471,761 Weidenbach Oct. 23, 1923 1,477,161 Aikman Dec. 11, 1923 1,653,110 Le Valley Dec. 20, 1927 1,996,620 Ketterer Apr. 2, 1935 1,997,184 Ruehman Apr. 9, 1935 2,055,578 Hurst Sept. 29, 1936 2,283,091 Johnson Nov. 18, 1941 2,294,609 Schlosser Sept. 1, 1942 2,301,435 Mercier Nov. 10, 1942 2,442,631 Winkler June 1, 1948 FOREIGN PATENTS Number Country Date 473,000 France 1914 551,252 France 1923 

